Exemplary embodiment of the invention relate to a fuel tank venting system for a motor vehicle and a method for diagnosing a fuel tank venting system.
The basic design of conventional fuel tank venting systems for motor vehicles and their function is described, for example, in ATZ Automobiltechnische Zeitschrift 101 (1999) 3, pages 166-173.
German patent document DE 10 2009 008 831 A1 discloses a fuel tank venting system of the generic kind. Upstream from a throttle valve, a first vent line is connected to an intake manifold of a motor vehicle via a first check valve. Downstream from the throttle valve, a second vent line is connected to the intake manifold via a second check valve. In this system, it is possible to detect leaks in the first or second vent line up to the position of the first check valve, using an intake manifold pressure sensor which is already present in the intake manifold. In this system configuration, a leak between the first check valve and the intake manifold cannot be detected. However, since the regulatory requirements in the United States stipulate that all types of leaks or blockages must be detectable unless components are connected via nondetachable connections, German patent document DE 10 2009 008 831 A1 proposes connecting the first check valve to the intake manifold via a nondetachable connection. For this purpose, the first check valve is positioned very closely to the intake manifold, at the end of the first vent line. This system has a drawback with regard to repair shop user-friendliness, since removal or replacement of the intake manifold can take place only together with the first check valve.
In addition, PCT publication WO 2009/106221 A1 discloses a check valve having a distance sensor, in which a movable part of the distance sensor is connected to a closing element of the check valve. The movable part may be a permanent magnet. A position of the permanent magnet, and thus of the closing element, may be measured using a Hall sensor. It is proposed to thus measure a volume flow of a fluid flowing through the check valve.
Exemplary embodiments of the present invention are directed to improving the repair shop user-friendliness of the generic fuel tank venting system while ensuring continued diagnostic capability in compliance with regulatory requirements.
The fuel tank venting system has an intake manifold for supplying air to a cylinder of an internal combustion engine of the motor vehicle, the intake manifold including a throttle valve and, upstream from the throttle valve, an air filter. In addition, the fuel tank venting system has a fuel tank, a tank vent valve, a cutoff valve, and an electronic control device, the electronic control device being connected to the throttle valve, the tank vent valve, and the cutoff valve, in each case for the purpose of controlled actuation. The control device may be a control unit or an assembly of multiple control units that are interconnected via communication connections. The connection between the electronic control device and the throttle valve, the tank vent valve, and the cutoff valve may be wired or wireless. Furthermore, the fuel tank venting system has a first vent line that includes a first check valve having a first closing element, and a second vent line, the cutoff valve being indirectly or directly connected to an inlet side of the tank vent valve, and an outlet side of the tank vent valve being connected to an inlet side of the first vent line and to an inlet side of the second vent line. The closing element of the check valve may be designed as a sphere, cone, flap, or diaphragm, or as some other known closing element.
An outlet side of the first vent line is connected to the intake manifold upstream from the throttle valve and downstream from the air filter, and an outlet side of the second vent line is connected to the intake manifold downstream from the throttle valve. The terms “upstream” and “downstream” refer to a direction of an air flow in the intake manifold.
According to the invention, a position sensor may be positioned at the first check valve for determining a position of a detectable element of the first closing element, the position sensor being connected to the electronic control device for the purpose of signal transmission. Here as well, the mentioned connection may be implemented in a wired or wireless manner.
In the mentioned system configuration, by means of the position sensor and the detectable element of the first check valve it is possible to detect leaks or obstructions in the first vent line. The leaks or obstructions may be detected over the entire distance between the tank vent valve, over the first vent line up to the intake manifold, i.e., up to the air filter.
A first advantageous refinement of the invention provides that the detectable element includes a magnet element, and the position sensor includes a Hall sensor. A magnet element may be mounted on or in the closing element in a cost-effective manner. A position of the magnet element, and thus of the first closing element, may be determined by means of the Hall sensor. In this case, the Hall sensor may be mounted in a flow channel of the check valve, or particularly advantageously, also outside the flow channel. A mounting outside the flow channel is cost-effective and robust.
The closing element is particularly advantageously designed in such a way that its position changes only in one direction during opening and closing, i.e., primarily in such a way that the closing element cannot rotate during opening and closing. This type of design is provided, for example, as a flap that is fastened on one side, or a diaphragm that is fastened on one side. Another advantageous refinement therefore provides that the first closing element includes a non-return flap. The non-return flap particularly advantageously has a leaf spring, the leaf spring exerting a force on the non-return flap in the direction of a closed position of the non-return flap. The check valve may thus be installed in the motor vehicle independently of position, since closing of the closing element occurs primarily due to an elastic force of the leaf spring, not due to gravity.
Another advantageous refinement provides that the second vent line includes a second check valve having a second closing element. In this case, a leak in the second vent line may advantageously be detected by means of an intake manifold pressure sensor situated in the intake manifold, downstream from the throttle valve or using the position sensor in the first check valve or a combination of both.
Another advantageous refinement provides that the first check valve and the second check valve are situated in a shared housing and form a double check valve, an inlet side of the double check valve at the same time forming the inlet side of the first vent line and the inlet side of the second vent line. Costs and space requirements may thus be reduced in the fuel tank venting system according to the invention.
Another advantageous refinement of the invention provides that a crankcase vent line is connected to the first vent line. This has the advantage that not only leaks in the first vent line, but also a disconnection or equivalent leaks of the crankcase vent line may be detected by means of the position sensor.
Another advantageous refinement of the invention provides that the intake manifold has a turbocharger upstream from the throttle valve. When the fuel tank venting system contains the turbocharger upstream from the throttle valve, there is no negative pressure in the intake manifold downstream from the throttle valve during full load operation of the internal combustion engine, and instead, there is a negative pressure upstream from the turbocharger. In this configuration, the first vent line opens into the intake manifold upstream from the turbocharger. Due to the negative pressure generated by the turbocharger under full load, leak detection may be carried out particularly easily by the position sensor.
The method for diagnosing a fuel tank venting system of a motor vehicle is characterized by a fuel tank venting system according to the invention, whereby a piece of error information is stored in the electronic control device, when a closed position of the first closing element is determined by means of the position sensor, and a full load regeneration operation is present, and a piece of error information is stored in the electronic control device when an open position of the first closing element (12) is determined by means of the position sensor and no full load regeneration operation is present.
The presence of a full load regeneration operation or a part-load regeneration operation is a function of a load on the internal combustion engine and a switching position of the tank vent valve, whereby the load on the internal combustion engine may be derived from measurement variables and/or control variables, for example a throttle valve position and engine speed. A full load regeneration operation is present when inlet manifold pressure is more than atmospheric pressure, and at the same time the tank vent valve is open. A part-load regeneration operation is present when inlet manifold pressure is less than the atmospheric pressure and at the same time the tank vent valve is open. The method is carried out according to the invention by means of the electronic control device, which is connected to all relevant electrical and electronic components and which has means for data processing.
A refinement of the method for diagnosing provides that the second vent line includes a second check valve having a second closing element, wherein
A leak and an obstruction of the second vent line may be reliably detected with the aid of the position sensor and the first detectable element.